Reinforcement Composition and Method Thereof

ABSTRACT

The present invention relates generally to a reinforcement composition and a method of reinforcing an asphalt cement concrete composition. The reinforcement composition includes a core and an outer container. The core includes a plurality of fibers, and the outer container includes a polyolefin selected from the group consisting of polyethylene, polypropylene, and mixtures thereof.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/539,823, filed Aug. 12, 2009 entitled “A Reinforcement Compositionand Method Thereof,” which is herein incorporated by reference in itsentirety.

FIELD OF THE INVENTION

The present invention relates to a reinforcement composition and amethod of reinforcing an asphalt cement concrete composition.

BACKGROUND OF THE INVENTION

It is known that the addition of a reinforcement component to buildingmaterials, such as concrete, including asphalt cement concrete andportland cement concrete and the like, can add strength, toughness, anddurability to improve the integrity of the material properties. Thereare a variety of reinforcement fiber additives known in the art that canprovide some of these characteristics to concrete building materials.Typical reinforcement materials that are added to concrete include, forexample, various gauges of wire mesh or reinforcement fibers, such as,asbestos fibers, glass fibers, steel fibers, mineral fibers, naturalfibers, synthetic fibers (such as polymer and aramid fibers), andcellulose fibers. A non-limiting example of suitable reinforcementfibers includes Basalt fibers. Some reinforcement fibers are bettersuited for particular applications than others. For example, asbestosfibers are known to provide effective reinforcement but, due toenvironmental and health concerns these fibers, are not extensivelyused. In addition, some fibers are relatively expensive.

Some advances have been made in the area of fiber reinforcement toprovide increased toughness and durability, and reduce cracking in thematrix of concrete building materials. However, the known reinforcingfibers have a number of disadvantages, such, as for example, it isdifficult to handle loose fibers and to control their introduction intoa concrete. It is desired to improve the ease of handling the fibers andfor the fibers to mix readily and distribute uniformly in a cementconcrete.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a reinforcement composition isprovided. The composition includes a core and an outer container; thecore including a plurality of fibers and the outer container comprisinga polyolefin selected from the group consisting of polyethylene,polypropylene, and mixtures thereof, wherein the core is containedwithin the outer container.

The plurality of fibers can be selected from the group consisting ofsynthetic fibers, natural fibers, and mixtures thereof. Further, thesynthetic fibers can be selected from the group consisting of polymerfibers, aramid fibers, and mixtures thereof. The polymer fibers can beselected from the group consisting of polyolefin fibers, polyamidefibers, polyvinyl-chloride fibers, and mixtures thereof. The polyolefinfibers can be selected from the group consisting of polypropylenefibers, polyethylene fibers, and mixtures thereof. The plurality offibers each or together can be configured in a predetermined number oftwists.

The outer container can also comprise amine. Furthermore, the outercontainer can comprise a plurality of fibers.

The plurality of fibers can be selected from the group consisting offibers that are meltable in an asphalt material, fibers that arenon-meltable in an asphalt material, and mixtures thereof.

The outer container can be dispersible, and further, can be dispersibleas a result of melting under heated conditions.

Another aspect of the present invention, provides a method ofreinforcing an asphalt composition including providing a containerhaving a core contained therein; the core comprising a plurality offibers, and the container comprising a polyolefin selected from thegroup consisting of polyethylene, polypropylene and mixtures thereof;introducing the container, aggregate, and binder into an asphalt-containing chamber; and forming an asphalt material.

The plurality of fibers can be selected from the group consisting ofsynthetic fibers, natural fibers, and mixtures thereof. Further, thesynthetic fibers can be selected from the group consisting of polymerfibers, aramid fibers, and mixtures thereof.

The container can further comprise a plurality of fibers.

The plurality of fibers can be present in an amount of from about 0.0001to about 10.0 percent by volume per ton of the asphalt material.

The container can be dispersed when a transition temperature of theouter container is reached or exceeded in the asphalt-containingchamber. The dispersed outer container can reduce the friability of theplurality of fibers in the asphalt-containing chamber.

The asphalt-containing chamber can be selected from the group consistingof an asphalt mixing machine and associated machines located up-line anddown-line of the asphalt mixing machine.

In an embodiment of the method of the present invention, more than onecontainer may be introduced into the asphalt-containing chamber.

The asphalt-containing chamber can be a component of a process selectedfrom the group consisting of a batch process and a continuous process.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a reinforcement composition forincorporation into an asphalt cement concrete composition. The presenceof the reinforcement composition can result in at least one change inthe strength, durability, toughness, integrity, and other materialproperties of the asphalt.

As used herein and the claims, the term “asphalt” means asphalt cementconcrete. Two types of cement are Portland cement and asphalt cement.The term “asphalt cement concrete” refers to the use of asphalt cement.The term “cement” refers to the binder that holds together the concrete.As used herein, the cement also can be referred to as “binder” or“liquid asphalt.” The term “concrete” refers to a gradation of fine andcoarse aggregate, such as, but not limited to sand and rock.

The reinforcement composition of the present invention includes a coreand an outer container. The core is encompassed by and contained withinthe outer container. The contents of the core includes a plurality offibers. Suitable fibers for use in the core can include a wide varietyof fibers known in the art to reinforce building materials, such asasphalt. The fibers can be synthetic or natural. Natural fibers caninclude wood-derivative fibers and mixtures thereof. Synthetic fiberscan include, but are not limited to, polymer fibers, aramid fibers, andmixtures thereof. Polymer fibers can include, but are not limited to,polyolefin fibers, such as polypropylene and polyethylene, polyamidefibers, polyvinyl-chloride fibers, and mixtures thereof. In oneembodiment of the present invention, the plurality of fibers in the coreinclude aramid fibers and a blend of polyolefin fibers. In anotherembodiment of the present invention, the aramid fibers are present in anamount of from 0 to about 100 percent by volume of the total fibers. Instill another embodiment of the present invention, the polyolefin fibersare present in an amount of from greater than 0 to 100 percent by volumeof the total fibers. The fibers can include a mixture of fibers thatmelt in the asphalt material and fibers that do not melt in the asphaltmaterial.

Suitable fibers for use in the present invention can be in a widevariety of shapes, sizes, and forms. In general, loose fibers aredifficult to handle, and therefore, it is desirable to configure andcontrol the fibers, such as to improve the ease of handling, e.g., foradding the fibers to the asphalt mixing process. Further, it isdesirable for the fibers to readily and uniformly disperse in theasphalt material within the asphalt mixing machine or associatedmachinery. Moreover, it is desirable to limit or reduce the friabilityof the fibers. For example, aramid fibers are known in the art to befriable and may generate dust, which can result in clogging of filtersin the asphalt mixing machine and related machinery.

The fibers, for example, can be flat, such as in the form of a sheet, orcylindrical, such as in the form of a tube or cord. The tubes or cordscan be bundled together in a circumferential wrap and cut to apredetermined length using conventional techniques and methods known forcutting fibers. The length of the fibers can vary widely, and the lengthcan be such that the fibers are dispersible in an asphalt material. Innon-limiting embodiments, the fibers may be cut into a length within therange of about 19 to 60 mm.

The fibers, individually or together in various combinations andproportions, can be fibrillated (i.e., pulled apart to form a net likestructure) or non-fibrillated. The fibers can be configured in apredetermined number of twists and turns. For example, the fiberssuitable for use in the present invention can include a fiber component,as disclosed in U.S. Pat. No. 7,168,232 (“the '232 patent”). The fibercomponent is a twisted bundle comprised of multiple strands of anon-fibrillating monofilament having a degree of twist greater thanabout 0.9 turns per inch. The '232 patent further discloses the twistedfiber component with another fiber component, discrete from the twistedfiber component, that is fibrillated. In U.S. Pat. No. 4,346,135, afibrous reinforcing means, including at least two various groups offibrous articles, is disclosed. At least one of the groups consists offibrous articles in the form of a closed filamentary net. In U.S. Pat.No. 6,753,081, a synthetic fiber blend is disclosed. The synthetic fiberblend includes a first fiber component formed of a homopolymerpolypropylene fiber, and a second fiber component is a copolymer formedof a polypropylene and a high-density polyethylene. The first fibercomponent is fibrillated, and the second fiber component is a twistedbundle of multiple strands of a non-fibrillating monofilament. Thedisclosures of U.S. Pat. Nos. 7,168,232; 6,753,081; and 4,346,135 areincorporated herein by reference.

The container of fibers can be added to the asphalt material in avariety of amounts. The amount can depend on various factors, such as,but not limited to, the particular fibers selected and the process usedto produce the asphalt material (e.g., batch or continuous). The amountof containers can be referred to as a dosage. One or more dosages can beadded to the asphalt material. For example, in one embodiment of thepresent invention, one dosage may be added per ton of asphalt material,and in another embodiment of the present invention, a plurality ofdosages may be added per ton of asphalt material. In alternateembodiments, the plurality of dosages can be combined or attachedtogether and added to the asphalt material. For example, the dosages canbe glued together.

The composition of the core can include various materials in addition tothe plurality of fibers. The materials can be in various forms, such as,but not limited to, pellets or powder. The materials can include, butare not limited to, chemical compounds that are typically used inpreparing asphalt and/or are known to provide advantages to the processand/or beneficial properties in the resultant asphalt material. Forexample, amine can be included in the core. The amine may be in the formof pellets or powder.

The outer container of the asphalt reinforcement composition of thepresent invention encompasses and contains or holds the core. The outercontainer is constructed of a material including, but not limited to,polyolefin. The polyolefin can be selected from a wide variety ofpolyolefins known in the art. Non-limiting examples of suitablepolyolefins can include, but are not limited to, polyethylene,polypropylene, and mixtures thereof. The composition of the outercontainer can further include other additives, such as those typicallyused in preparing an asphalt material and/or those known to produceadvantages to the process and/or beneficial properties in the resultantasphalt material. Without intending to be bound by any theory, it isbelieved that, upon dispersal of the outer container, the materials ofwhich the outer container is constructed will be dispersed into theasphalt material, and therefore, any additives that are typicallyincluded in the asphalt material can be included in the composition ofthe outer container. In one embodiment of the present invention, theouter container includes amine. The amine can be selected from a widevariety of amines known in the art. In another embodiment of the presentinvention, the outer container can include fibers. Suitable fibers foruse in the outer container can be selected from those previouslydisclosed herein. The fibers in the outer container can be the same asor different from the fibers in the core.

The asphalt reinforcement composition of the present invention isintroduced into the asphalt material prior to field placement. Thereinforcement composition can be introduced into the asphalt materialduring various steps in the manufacture process. For example, thereinforcement composition can be added in an asphalt mixing machine orassociated machinery, or in a hopper, or in a transportation vehicle, orafter discharge from the mixing machine or associated machinery, or thehopper or the transportation vehicle. The reinforcement composition canbe added at various steps in the process provided that there issufficient mixing that occurs at the various steps in the process priorto field placement to incorporate the reinforcement composition into theasphalt material.

In addition to the asphalt reinforcement composition, compounds used inproducing an asphalt material include, but are not limited to, aggregateand binder, such as liquid asphalt. Other additives may also be added tothe asphalt material (for example, in the asphalt mixing machine), suchas, for example, lime powder. The process of manufacturing an asphaltmaterial can include a batch or continuous process. As described above,the asphalt reinforcement composition can be added to the asphaltmaterial during the manufacturing process prior to field placement. Forexample, in an embodiment of the batch process, the asphaltreinforcement composition can be added to the mixing chamber, havingmixing blades, of the asphalt mixing machine prior to introducingaggregate and liquid asphalt. For example, in an embodiment of thecontinuous process, wherein a drum mixer is used, the asphaltreinforcement composition can be added to the process at any time priorto the introduction of liquid asphalt. The manufacture of an asphaltmaterial consists of a thermal process, and therefore, includes heatingthe ingredients, such as in the chamber of the asphalt mixing machine.The temperature of the asphalt material can vary and can include thosetemperatures typically used in commercially-operated asphaltmanufacturing facilities. In an embodiment of the present invention, thetemperature can be within a range of about 212° F. to 375° F., or higherthan 700° F.

The outer container of the asphalt reinforcement composition isdispersible in the asphalt material. In alternate embodiments of theprocess of the present invention, the reinforcement composition can bedispersed in the asphalt material in the asphalt mixing machine, or inassociated machinery located either up-line or down-line from the mixingmachine. In one embodiment of the present invention, the outer containerdisperses as a result of melting. The transition temperature of theouter container, i.e., the temperature at which the outer containermelts or dissolves, such as its melting point, can depend on thecomposition of the outer container, e.g., the materials from which theouter container is made. As the transition temperature is reached orexceeded in the asphalt or in the chamber containing the asphalt, suchas the asphalt mixing machine, the outer container melts and isdispersed within the asphalt material. The transition temperature can bereached or exceeded, and the outer container can melt and be dispersedbefore, during, or after the mixing of the asphalt material. Further,upon dispersal of the outer container, the fibers contained within thecore are released and mixed into the asphalt material. The fibers mayhave a transition temperature such that they may or may not be meltablewithin the asphalt material. The asphalt reinforcement composition canbe added to the asphalt material in varying amounts. Typically, theamount added is such that desired properties of the asphalt material areachieved. The amount of the reinforcement composition used can depend onthe composition of the core, the composition of the outer containerand/or various processing conditions employed. In an embodiment of thepresent invention, fibers can be added to the asphalt material in anamount such that the fibers provided from the core, or the outercontainer, or a combination thereof, is greater than zero. In anotherembodiment, the fibers from the core, outer container, or combinationthereof, can be at least 10.0 percent or greater by volume per ton ofasphalt material. In yet another embodiment of the present invention,the fibers from the core, outer container, or combination thereof can bein a range of from about 0.0001 percent to about 5.0 percent by volumeper ton of the asphalt material.

Without intending to be bound by any theory, it is believed thatintroduction of the fibers into the asphalt material in accordance withthe asphalt reinforcement composition of the present invention (i.e.,outer container and core configuration) will result in less entanglementand less clumping of the fibers as compared to the fibers beingintroduced loosely into the asphalt or chamber containing the asphalt(e.g., asphalt mixing machine). Further, it is believed that, sincethere is less entanglement and less clumping of the fibers, a lesseramount of fibers will need to be added to the asphalt material whenemploying the asphalt reinforcement composition of the present inventioninstead of loosely adding the fibers.

Further, without intending to be bound by any theory, it is believedthat melting of the outer container and/or core may limit or reduce thefriability of the fibers, such as, for example, aramid fibers, and mayimprove the random dispersibility of non-melting fibers used in theasphalt reinforcement composition.

By way of example, the asphalt reinforcement composition of the presentinvention can be incorporated into the manufacture of various asphaltbuilding materials and products used for building or construction, suchas, for example, structural pavements, airport runways and tarmacs,bridge deck overlays, floors, and pre-cast asphalt products. The asphaltreinforcement composition of the present invention may also be used forrepair, rehabilitation, retrofit, and renovation of existing products orstructures, such as, for example, in overlays, and repairs of airportpavements, bridge decks, parking areas, roadways, and the like,including patching and filling potholes.

In addition to reinforcement, the incorporation of the asphaltreinforcement composition of the present invention in, for example, castasphalt material, modifies the cracking mechanism and reduces thepropagation of micro-cracking caused by shrinkage. It is believed thatrelative to non-reinforced asphalt, the resultant cracks of fiberreinforced concrete of the present invention are smaller in width, thepermeability of the material is reduced, and the ultimate crackingstrain is enhanced. Furthermore, the fibers employed in the presentinvention are capable of carrying a load across the crack. As a result,the asphalt material may have at least one change in its materialproperties, such as toughness, residual load carrying ability after thefirst crack, and impact resistance. Moreover, it is believed that thefibers used in the present invention produce an asphalt material havingimproved strength compared to non-reinforced asphalt, such that theasphalt material of the present invention can be suitable for locationswhere the asphalt will experience both high and low temperatures andareas subjected to heavy loadings (e.g., high traffic areas) and heavyconcentrations of truck traffic as well as many other uses.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of the invention which is to be given thefull breadth of the claims appended and any and all equivalents thereof.

1. A reinforcement composition comprising a core and an outer container,the core comprising a plurality of fibers and the outer containercomprising a polyolefin selected from the group consisting ofpolyethylene, polypropylene, and mixtures thereof, wherein the core iscontained within the outer containment.
 2. The reinforcement compositionof claim 1, wherein the plurality of fibers is selected from the groupconsisting of synthetic fibers, natural fibers, and mixtures thereof. 3.The reinforcement composition of claim 2, wherein the synthetic fibersare selected from the group consisting of polymer fibers, aramid fibers,and mixtures thereof.
 4. The reinforcement composition of claim 3,wherein the polymer fibers are selected from the group consisting ofpolyolefin fibers, polyamide fibers, polyvinyl-chloride fibers, andmixtures thereof.
 5. The reinforcement composition of claim 4, whereinthe polyolefin fibers are selected from the group consisting ofpolypropylene fibers, polyethylene fibers, and mixtures thereof.
 6. Thereinforcement composition of claim 1, wherein the plurality of fibersare each or together configured in a predetermined number of twists. 7.The reinforcement composition of claim 1, wherein the outer containerfurther comprises amine.
 8. The reinforcement composition of claim 1,wherein the outer container further comprises a plurality of fibers. 9.The reinforcement composition of claim 1, wherein the plurality offibers is selected from the group consisting of fibers that are meltablein an asphalt material, fibers that are non-meltable in an asphaltmaterial, and mixtures thereof.
 10. The reinforcement composition ofclaim 1, wherein the outer container is dispersible.
 11. Thereinforcement composition of claim 10, wherein the outer containmentmaterial is dispersible by melting.